The present invention relates in general to ballistic projectiles, and in particular to a new and useful projectile configuration having a subcaliber rear section which increases aerodynamic stability.
So-called "long rod" projectiles are stabilized by external fins or supercaliber flare skirts, which employ aerodynamic lift at the aft section to "right" the projectile with the trajectory as it oscillates slightly out of axial alignment with the oncoming airstream. This constitutes a static stabilization since the distribution of static pressure over the projectile results in a self-compensating aerodynamic moment acting in the neutralizing sense.
So called "short" projectiles must be spinned at very high rates utilizing rifling of a gun tube to thereby acquire gyroscopic stability which maintains the alignment of the projectile axis. Short projectiles are inherently statically unstable. An upper geometric limit on spin stabilization is reached at a length to diameter ratio of approximately seven. Separately, an upper limit on spin is imposed by the appearance of unfavorable dynamics such as Magnus effect and damping.
Long rod projectiles require sabots to fill the annular void necessarily created by the difference in diameter between the fin span and the projectile. Alternately, a complex mechanical folding and deployment mechanism is utilized for the fin stabilizers.
On the other hand, short projectiles must be designed to operate in the restricted spin range and are further constrained to the available rifle twists.
U.S. Pat. No. 4,195,573 to Leeker et al. discloses a flare stabilized projectile having flow passages through the skirt. A sabot is utilized on the forward part of the projectile body which is equal in outer diameter to the skirt so that only a subcaliber projectile can be accommodated.
U.S. Pat. No. 3,620,167 is also pertinent for showing a tail stabilizer. The main body of the projectile having a maximum caliber size diameter does not however, taper in one direction toward the tail stabilizer with the tail stabilizer tapering outwardly in an opposite direction.
U.S. Pat. No. 3,745,926 to Mertz et al discloses a long-rod projectile with spin stabilization utilizing a boat-tail type rear section which may contribute to decreasing static stability.
U.S. Pat. No. 3,081,703 to Kamp et al discloses an expandable flared control system for stabilizing a projectile.